This application claims the priority of German patent document 103 08 256.5, filed Feb. 25, 2003 (PCT International Application No. PCT/EP2004/001138, filed Feb. 7, 2003), the disclosure of which is expressly incorporated by reference herein.
The invention relates to a method for operating a traffic-adaptive assistance system in a vehicle (the “host vehicle”), which uses speed-related and/or distance-related variables of the host vehicle and of a preceding vehicle to accelerate or decelerate the host vehicle.
In a method of this type disclosed in German patent document DE 10019190 A1, the value of the acceleration or deceleration of a vehicle is limited by the traffic-adaptive assistance system using a lower and/or upper limits. European patent document EP 0443644 A1, on the other hand, proposes to actuate a traffic-adaptive assistance system using a target distance, while European patent document EP 1063626 A1 discloses actuating a traffic-adaptive assistance system with different individual time intervals or distances relative to a preceding vehicle. In European patent document EP 1225079 A2, a traffic-adaptive assistance system is actuated based on a target distance of a vehicle from a preceding vehicle.
One object of the present invention is to provide a method for actuating a traffic-adaptive assistance system which is flexible, behaves in a manner that emulates the behavior of real vehicle drivers, and achieves good reaction times.
This and other objects and advantages are achieved by the method according to the invention, in which the traffic-adaptive assistance system is actuated without regard to any target time interval or target distance, if the actual time interval and/or the actual distance between the host vehicle and the preceding vehicle is greater than a predefinable respective lower limiting value and smaller than a predefinable respective upper limiting value.
The invention in effect ‘automatically” takes into account the prevailing traffic situation and the travel history of the host vehicle (for example the driving behavior in the last ten minutes) during the operation of the traffic-adaptive assistance system. This is because, if the actual time interval or the actual distance between the host vehicle and the preceding vehicle is within predefinable limiting values (that is, greater than the predefinable lower limiting value and smaller than the predefinable upper limiting value, as noted above), control of the traffic-adaptive assistance system based on a target time interval or target distance is dispensed with or suppressed, thereby achieving a particularly flexible actuation. In this context, alternatively either just one actual time interval or just one actual distance or a combination of the two is provided, while a situation-dependent selection may also be provided in the vehicle.
While the methods presented in the prior art for operating traffic-adaptive assistance systems influence the “effects” of its actuation (for example, an acceleration value determined by the traffic-adaptive assistance system is limited), the invention intervenes earlier, with regard to the “causes”, by directly selecting the variables which are provided for the actuation of the traffic-adaptive assistance system. In other words, with the method according to the invention it become possible to introduce an additional “degree of freedom” by dispensing with the use of a target time interval or distance for the purpose of actuation. Thus, allowance is made for the prevailing traffic situation in that the time interval (or the distance) which then exists between the two vehicles after an acceleration or deceleration of the vehicle has ended is not predetermined by the traffic-adaptive assistance system (i.e., for when a differential speed of virtually zero is present between the vehicle and the preceding vehicle).
In the methods which are presented in the prior art for actuating traffic-adaptive assistance systems, fixed time intervals and distances which are determined according to fixedly predefined relationships, and are always maintained. In contrast, a time interval or distance which is achieved according to the invention as a result of an acceleration process or deceleration process of the vehicle is the consequence of a respective traffic situation and/or of a respective vehicle history. This is an impressive indication of the behavior of the method according to the invention which is adapted to the properties of real vehicle drivers. This is because even though, according to the invention, the time interval or the distance can assume any desired value between the predefinable lower and upper limiting values (i.e., selection from an infinitely large number of values), in the methods presented in the prior art these are only a single discrete value or a small number of discrete values.
One particularly simple embodiment of the invention is obtained if either or both of the lower and upper limiting values is implemented as a constant. As a result, necessary calculations can be carried out particularly quickly, and in a traceable fashion.
The invention can be applied even more flexibly if one or both limiting values can be predefined as a function of the speed of the host vehicle and/or of the speed of a further vehicle (for example, a preceding vehicle), which permits the respective traffic situation to be taken into account.
In one particularly advantageous embodiment of the invention, the lower and/or upper limiting values are predefinable as a function of the type of “traffic state phase” prevailing at the position of the host vehicle. (Traffic state phases distinguish the prevailing traffic state in a particularly easy way. One traffic state phase is, for example, compressed synchronized traffic. These traffic state phases are explained in more detail in the three phase theory of traffic, see for example B. S. Kerner, Phys. Rev. E Vol. 65, 046138, 2002.)
A particularly large degree of flexibility of the invention is obtained if the lower limiting value and/or the upper limiting value can be predefined as a function of the chronological/spatial distribution of the traffic in the surroundings of the host vehicle. A chronological distribution is, for example, a predicted (chronological) development of the traffic, a spatial distribution is, for example, a (spatial) change, i.e., a gradient, in the speed and/or the traffic density in front of the host vehicle. The surroundings of the vehicle extend, for example, over an area of 300 to 500 meters. Smaller surroundings can also be provided. Surroundings comprise here not only the lane on which the host vehicle is located but also secondary lanes.
One particularly advantageous embodiment uses only the differential speed of the vehicles to actuate the traffic-adaptive assistance system. This ensures that the actuation is efficient, and at the same time particularly simple and easy to handle in terms of computing technology.
If the actual time interval or distance between the host vehicle and the preceding vehicle is smaller than the predefinable lower limiting value, the traffic-adaptive assistance system preferably decelerates the vehicle. On the other hand, the actual time interval or distance is greater than the predefinable upper limiting value, the traffic-adaptive assistance system will preferably accelerates the vehicle.
In one advantageous embodiment of the invention, the traffic-adaptive assistance system is additionally actuated based on the distance from at least one further vehicle. This further vehicle may be, for example, a vehicle which is located next to the vehicle in an adjacent lane.
In a further advantageous embodiment of the invention, the traffic-adaptive assistance system is also actuated based on the speed of at least one further vehicle (for example, a vehicle next to the vehicle in an adjacent lane.
In one embodiment, the method according to the invention is preferably implemented in the form of a computer program, which is carried out when the program is run on a computer.
A further preferred embodiment of the invention is in the form of a computer program product comprising a computer program stored on a computer-readable data carrier to carry out the method according to the invention when the program is run on a computer.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.